Insulator.



Patented Aug. 13, 1912.

L. MGCARTHY.

INSULATOR.

APPLIUATION FILED 11111.21, 1911.

t STATES PATENT OFFICE.

Louis MUCARTHY, or Bos'roN, MASSACHUSETTS.

' INSULATOR.

To all whom it may concern:

Beit known that I, Louis MoCAn'rHY, citizen of the United States, residing at Boston, county of Suifolk, and State of Massachusetts, have invented a certain new and useful Improvement in Insulators, of which the following is a specification, reference being had therein to the accompanying drawings.

My present invention has for its object a new and improved insulator capable of withstanding an electric. current of relatively high voltage and of being made in various forms. Some of these forms are insulating couplings to be used tosupport electroliers, electric light fixtures and the like; ball strains; and trolley wire insulators, the principle of operation being the same in all forms.

It is well known to those skilled in the art that natural mica constitutes an insulating material of great excellence', and it has been usually utilized in insulators either in superposed layers in its natural state or in a comminuted state mixed with some suitable gum, such as sliellac and forming a. composition capable of bein molded. It has been found `however' that w 'en the .first of these methods is employed, there is a tendency for the electric current to follow the air spaces in -the layers of mica. This diliiculty is obviated by the use of the molded composition but on the other hand the molded composi Ation does not have as high resistance.

`It has also been found that if leaves of natural mica are carefully overlapped so as to break joints and are held together by some suitable insulating adhesive such as shellac, the whole being subjected to pressure, an insulating material is .formed which has a much greater insulating power than either natural mica or molded mica composition. The great advantages of this kind of insulation, however, have never been made use of in insulators of the types referred to above.

The insulator embodying the present. in-

'vention is constructed by forming a tube of i the said insulating material by overlapping leaves of mica held. together b a suitable insulating adhesive such 'as shel acg. then inserting the tube thus formed ink a vsuitable metallic shell and put-ting in place the end .members and a suitable insulating washer between the opposing faces of the end members, and then contracting the metallic shell .onto the inclosedpartsY 1n the .presence of Specification of Letters Patent.

Application'led January 21, 1911.

Patented Aug. 13, 1912.

Serial No. 603,835.

heat thereby solidifying the insulation and converting the parts into a substantially unitary structure. In practice, I find it convenient to make up the insulating material in the'form of flat sheets, which when heated may be rolled into the shape of a tube. In testing insulators made in this manner, it is found that the electric current which tends to run' through the washer between the end members comes against the wall of the tube of overlapped leaves of mica which are practically impenetrable to .the electric current, and that the electric current will jump across the outside of the insulator before the insulating tube will be punctured.

The invention will be fully understood from the following description taken in connection with the accompanying drawings and the novel features will be pointed out and clearly defined in the claims at the close of the specification.

In the drawings,-Figure 1 is an elevation of an insulator embodying my invention. Fig. 2 is a vertical section of the insulator shown in Fig. l. Figs. 3 to 5 inclusive illustrate the successive steps in the process of making the insulator shown in Figs. 1 and 2. Fig. 6 is a section of` another form of insulator embodying my invention.

Referring now to the drawings, and particularly to Fig. 3, there is shown at 12, a flat sheet of insulatin material composed of many .thin leaves lo posed and overlapping and held together by a suitable insulating adhesive such as a solution of shellac, the whole being'compressed in the presence of heat to densify it. This insulating material in flat sheets is a well known article of commerce, sometimes called micanite or compressed mica. Therefore it will not be described at greater length. This sheet is then heated, preferably on a hot natural mica super table, suiiiciently to soften the insulating adtallic shell 15 (see- Fig. 5), and the twol metallic end membersl and 17 separated by a washer 18 of insulating material are put in place within the tube 14. The washer 18 is preferably Vcut from a. sheet of the insu lating material, of the kind already de.g

scribed; The two end members are prefer ably made in the form of a frustum of a cone and placed base to base for a reason to ...gua

be laterl explained. The parts thus assembled are then preferably heated suiiicxently to soften the insulating adhesive contained in the insulating materlal and the whole is ished insulator under pressure from the me,

tallic shell. The pressure applied to form the shell also draws the proximate faces of the end members 16 and 17 closer together by reason of the conical shape of the'end members and so compresses the washer 18 of insulation between the two end melnbers causing the washer to lll completely any irregularities inthe proximate faces of the end members. By this step the separate parts of the insulator are converted into a rigid unitary whole having ood mechanical strength. I believethat t e forming of the insulation under pressure and in the presence of heat su cient tol soft-en the insulating adhesive d s not do injury to the individual leaves'o mica forming the insulation, but that these leaves slide slightly 4on each other so that in its finished condition the leaves' of mica stillv overlap each other I and present a nearly impenetrable obstruction to the electric current.

The insulator may afterward be covered with plastic insulating material inthe well known manner if desired. A covered insulating joint is shown in Fig. 6, the cover-i1 being designated 21. In this insulator the end members 22 and 23 are made somewhat longer. V

What I claim is v 1. The improved insulator comprising two end members, a washer of 'insulating mate- .rial separating the opposing faces of said end members, a tube surrounding said end members and composed of a. sheet of overlapping leaves of mica wound upon itself in convoluted form, so as to provide a plurality of superposed la ers of said sheet with the ,extended sur acesof the mica leaves arranged substantially transverseto the natural or disposed direction of liow of the current, andwa shell outside of thel said .tube.

2; .The improved insulator comprising two end members, a washer .of insulating mate' rial separating the opposing faces of said end members, a tube surrounding said end members and composei .of a sheet of overlapping leaves ofV mica wound upon itself 1n convoluted form, so as to provlde a plurality of superposed layers of said sheet,

and a shell outside of the said tube, said shell being contracted at its ends so as to subject said convolutedtube to heavy pressure between itself and said end members.

The herein described improved insulator consisting of inwardly lenlarged end members with theirY bases toward but separated from each other, a shell encircling said end members, a tube of insulatin materiall interposed between said shell an said end lmembers and com osed of overlapping leaves of'inica adheslvely held together, and with the extended surfaces of the mica leaves arranged substantially transverse to the direction of iiow of the current, a washer of insulating material' interposed between said end members and also composed of overlapping leaves of mica adhesivelyfheld together, with the surfaces of the mica leaves also transverse to the direction of flow of the current, said shell being contracted at its ends and thereby tightly gripping the said tube of insulating material, so as to hold the same against the said end members under heavy pressure.

4. The herein described improved insulator consisting of inwardly enlarged end members with their bases Qtoward but separated from each other, a shell encircling said end members, a tube of insulating material interposed between said shell and said end members and composed of a plurality of convoluted layers of overlapping leaves of mica adhesively held together, and with the linsulatinr material interposed between said end members and also composed of aplulrality of layers of overlapping leaves of mica adhesively held together, with the surfaces of the mica leaves also transverse to the direction of iow of the current, said shell being contracted to its ends and thereby tightly ripping the said tube of insulating .materia so as to hold the same ragainstl the said end members under heavy pressure.

In testimon whereof'I affix my signature, in presence o two witnesses.

y LOUIS MCCARTHY. Witnesses: v

Gramm W. Pnou'rr, LLorD Dorr. 

